This invention is directed to disposable articles made from a water soluble polymer, a surface of said article coated with a degradable water-insoluble polymer. The disposable articles include diapers; catamenial devices, such as tampons and applicator tubes for tampons, and sanitary napkins; hospital bed liners; bandages, and the like. Additionally, where an article is subject to outdoor exposure, the article made from the water soluble polymer is coated with the degradable water-insoluble polymer which provides moisture protection for the water soluble polymer until the degradable polymer becomes embrittled by, for example, photo-oxidative degradation. Additionally, such an article, if buried underground, may be biodegraded by microorganisms such as molds, bacterial, etc. Such articles are useful as tapes which contain seeds, carriers for fertilizers, fungicides, pesticides, and the like.
Further, the present invention is directed to a disposable substrate, in the form of, for example, a sheet or film, made from a water soluble polymer, a surface of said substrate coated with a degradable water-insoluble polymer. Such a disposable substrate may be used to contain a liquid or to contain absorbent materials, etc.
Disposable absorbent articles made from water soluble polymers are well known. U.S. Pat. No. 3,783,872, for example, crosslinks an aqueous solution of a poly(ethylene oxide) homopolymer to a hydrophilic water-insoluble poly(ethylene oxide) polymer by utilizing ionizing radiation. These polymers, as stated in U.S. Pat. No. 3,783,872, possess the ability to incorporate large amounts of water and are insoluble in water, irrespective of temperature, and retain liquids, solutions and suspensions.
Additionally, U.S. Pat. No. 3,957,605 cocrosslinks poly(ethylene oxide) and at least one other water soluble polymer by exposing aqueous systems of the polymers to high energy irradiation. The resulting products are insoluble hydrophilic gels which can contain, or when dried, absorb large quantities of aqueous fluids and are useful for absorbing media for disposable absorbent articles such as diapers, sanitary napkins, and the like.
However, since the products are insoluble they cannot be conveniently disposed of into, for example, waste water systems, since they do not disoolve therein.
If the disposable article is made from a water soluble polymer, such as poly(ethylene oxide), its utility, in most cases, is limited to application where it will not be in contact with a liquid medium. Due to the water sensitivity of the polymer, even casual contact with moisture will cause the surface of the article to become tacky or slippery, which interferes with the proper function of the article.
Thus, there exists a need to treat the disposable article made from the water soluble polymer to decrease its water sensitivity, yet not render it water insoluble, so that it can be conveniently disposed of into, for example, waste water systems.
U.S. Pat. No. 3,197,332 describes a method for rendering films or shaped articles made from polyethylene oxide polymers water-resistant. A sheet of ethylene oxide polymer is coated on one side with a relatively thin coating of a silicon compound. The coated side of the sheet is water resistant, while if water is applied to the other side, the entire sheet will collapse. However, the silicon coating is not degradable and may be objectionable when disposed of into, for example, waste water systems. Also, the silicon coating may be objectionable when in contact with delicate body tissues.